PURPOSE: Despite the reduced incidence and mortality of gastric cancer, this illness still remains the second leading cause of cancer death in Korea. Various adjuvant chemotherapies have been proposed for patients with advanced gastric cancer. Randomized trials comparing chemotherapies with best supportive care have consistently shown that cytotoxic treatment is of some benefit. Nevertheless, there has been no major improvement in the overall prognosis of advanced gastric cancer. METHODS: We have examined the chemotherapy sensitivity of advanced gastric cancer specimens by using an ex vivo ATP based chemosensitivity assay (ATP-TCA). A variety of chemotherapeutic agents were tested. The one hundred and forty specimens we tested were from resection specimens. RESULTS: The histological tumor classification, lymphatic invasion, neural invasion and venous invasion affected the chemosensitivity of some drugs. 5-FU was a more potent drug than cisplatin, doxorubicin, iriontecan and methotrexate. The chemosensitivity of differentiated cancer was different compared to that of undifferentiated cancer. Doxorubicin and iriontecan were more effective in poorly differentiated, signet ring cell and diffuse type cancers. The manner of tumor invasion affected the chemosensitivity to some drugs. CONCLUSISON: Further study is necessary to assess the effectiveness of some chemotherapy drugs on advanced gastric cancer, including their effect on tumor recurrence and patient survival.